After upgrading TYPO3 from 8 to 9,10,11,12 and also Mask to version 8.2.6 i got the following error/issue.
BE: Mask-Module: Some Mask-Elements are empty
If I edit this empty Elements i got the following error within TYPO3-Log:
Core: Exception handler (WEB): Uncaught TYPO3 Exception: #1476107295: PHP Warning: Undefined array key "imageoverlayPalette" in /.../httpdocs/typo3conf/ext/mask/Classes/Controller/FieldsController.php line 163 | TYPO3\CMS\Core\Error\Exception thrown in file /.../httpdocs/typo3/sysext/core/Classes/Error/ErrorHandler.php in line 138. Requested URL: https://www.mydomain.de/typo3/ajax/mask/loadElement?token=--AnonymizedToken--&type=tt_content&key=hlg_fullwidth_bg_img_list
THX in advance for help